Numerical study of granular debris flow run-up against slit dams by discrete element method

Run-up of granular debris flows against slit dams on slopes is a complex process that involves deceleration, deposition, and discharge. It is imperative to understand the run-up mechanism and to predict the maximum run-up height for the engineering design and hazard mitigation. However, the interaction between granular flows and slit dams, which significantly affects the run-up height, is still not well understood. In this study, an analytical model based on the momentum approach was derived to predict the run-up heights of granular debris flows. A numerical investigation of granular debris flow impacting slit dams using the discrete element method (DEM) was then conducted. The influence of the Froude number (N-Fr) and the relative post spacing (R) on run-up height were studied. This study illustrates that the analytical model based on the momentum approach can predict the run-up heights well within a certain range of Froude numbers. There is a critical value of relative post spacing (R-C): within the critical value, the maximum run-up height is insensitive to the relative post spacing; once R exceeds the critical value, the maximum run-up height decreases rapidly as the relative post spacing increases.